부산대학교 도서관

Acyclovir dosage should be adjusted based on renal function. Neurotoxicity is a rare adverse effect and occurs mostly in patients with renal insufficiency. Furthermore, neurologic symptoms may occur even after dosage adjustment according to current recommendations. Additionally, making a differential diagnosis between viral encephalitis and drug-induced neurotoxicity is difficult. Therefore, therapeutic drug monitoring of acyclovir might be a feasible approach to guide the following management. A 59-year-old woman with a medical history of end-stage renal disease, type 2 diabetes mellitus, hypertension, dyslipidemia, hyperthyroidism, and anemia undergoing peritoneal dialysis was prescribed oral acyclovir (800 mg Q12H) for the treatment of herpes zoster infection. She was admitted to the emergency department due to neurologic symptoms, including slurred speech, disorientation, and unstable gait, and she was suspected to have acyclovir toxicity. Because there was no improvement after stopping taking acyclovir, hemodialysis was initiated. After the first session of hemodialysis, serum concentrations of acyclovir and its metabolite 9-Carboxymethoxymethylguanine decreased from 3.61 and 18.82 μg/mL to 1.70 and 4.06 μg/mL, respectively. Her neurologic status returned to baseline gradually, and peritoneal dialysis was resumed after three hemodialysis sessions. On the Naranjo scale, the probability of an adverse drug reaction was 6. Acyclovir dosage should be adjusted promptly in accordance with renal function in patients with renal insufficiency. In addition to therapeutic effects, adverse events should be monitored closely during the treatment period. When neurologic symptoms appear after acyclovir administration, therapeutic drug monitoring could be helpful for making a differential diagnosis to guide future patient management.